1. Field of the Invention
The present invention relates to a pneumatic tire which is provided on a tread surface with a plurality of main grooves extending along a tire circumferential direction, and shoulder lateral grooves extending to an outer side in a tire width direction from the shoulder main grooves positioned in an outermost side in the tire width direction among these main grooves.
2. Description of the Related Art
On a tread surface of a general pneumatic tire, there are provided with a plurality of main grooves extending along a tire circumferential direction, and lateral grooves extending so as to intersect the main grooves. In the pneumatic tire mentioned above, there may be generated a so-called biased abrasion, that is, a phenomenon in which a tread surface coming into contact with a road surface wears partly by priority without wearing uniformly.
On the basis of the main groove (which may be called as the shoulder main groove) which is positioned in the outermost side in the tire width direction among a plurality of main grooves, on the assumption that an inner side thereof is a center region, and an outer side thereof is a shoulder region, a shoulder abrasion that the shoulder region wears by priority may be generated, and a biased abrasion in the tire width direction may be generated. As a result of an analysis by the inventors of the present invention, there has been found that a ground contact pressure in the shoulder region is comparatively higher in comparison with the center region, particularly at a time of braking, and an unevenness of the ground contact pressure mentioned above causes the shoulder abrasion.
The following Japanese Unexamined Patent Publication No. 2004-351991 discloses a pneumatic tire which is provided with a projection in a side wall having a greater deformation, in two side walls of a lateral groove, and can suppress a deformation of the side wall by bringing the projection into contact with the opposed side wall even if the side walls deform. However, the pneumatic tire in accordance with the Japanese Unexamined Patent Publication No. 2004-351991 aims at suppressing a heel and toe abrasion, and does not aim at suppressing a shoulder abrasion caused by the unevenness of the ground contact pressure mentioned above.
Further, in the pneumatic tire, since a groove volumetric capacity is reduced by a progress of he abrasion, a drainage performance is lowered in conjunction with the progress of the abrasion. In the pneumatic tire described in the Japanese Unexamined Patent Publication No. 2004-351991, since the projection reduces the groove volumetric capacity of the lateral groove, the drainage performance tends to be further deteriorated.